A technique called optogenetics has transformed neuroscience during the past 10 years by allowing researchers to turn specific neurons on and off in experimental animals. By flipping these neural switches, it has provided clues about which brain pathways are involved in diseases like depression and obsessive-compulsive disorder. “Optogenetics is not just a flash in the pan,” saysneuroscientist Robert Gereau of Washington University in Saint Louis. “It allows us to do experiments that were not doable before. This is a true game changer like few other techniques in science.”

Since the first papers were published on optogenetics in the mid-aughts some researchers have mused about one day using optogenetics in patients, imagining the possibility of an off-switch for depression, for instance.